This invention relates to information storage devices and more particularly to storage devices of the credit card type which can be carried in the wallet but which can store a substantial quantity information.
IC cards are available which incorporate an onboard microprocessor and an onboard semiconductor memory. Those cards have substantially increased the amount and flexibility of information which can be recorded in a carry-around wallet-sized device, but are still limited in the amount of information which can be stored and the cost per unit information for such storage. More particularly, while semiconductor memories can be considered to be "inexpensive" in the context of providing operating memory in a computer, they are not quite so "inexpensive" when considered in the context of an ultimately disposable credit card of the type issued in large numbers, and having a life span of say a few years.
One of the more inexpensive types of credit cards is the magnetic stripe card with which the public is generally familiar. It has no onboard processing power, but only a magnetic stripe which records certain limited information, typically recorded prior to issuance, and which information is typically not changed for the life of the card. In that environment, the recorded information usually relates to the identity of the user and the identity of the type of transaction which the card is designed to perform, but there is little additional information and no possibility of writing new information onto the card after issuance. While such cards have served their purpose, it is desirable in many instances to provide a card with additional mass storage capability, but which still possesses some of the security characteristics which prevent readout of the information except by authorized parties and on authorized terminals.
Mass storage devices are available such as optical recording media or large-scale magnetic recording media, but their drawback in the present context is the insecure method of recording--i.e., once the information is recorded it can be read out by anyone having access to the storage medium. Thus, while such mass storage devices have the attractive feature of providing a low cost per unit of information stored, they do not have the security associated with the microprocessor controlled semiconductor memory.